Electromagnet valve, in particular for automatic gearboxes

ABSTRACT

The invention proposes a solenoid valve ( 10 ), in particular for automatic transmissions of motor vehicles. Solenoid valves ( 10 ) have the problem of vibrations that detract from shifting comfort. Integrating a throttle restriction ( 52 ) into the solenoid valve ( 10 ) on the part of the solenoid valve ( 10 ) oriented toward the consumer as proposed by the invention makes it possible to efficiently reduce such vibrations. In addition, the production costs are low, in particular because the throttle restriction ( 52 ) is provided In a filter cage ( 44 ) of the solenoid valve ( 10 ).

BACKGROUND OF THE INVENTION

The invention is based on a solenoid valve, in particular for automatictransmissions, as is known, for example, from DE 197 33 660 A1.

In the hydraulic control of automatic transmissions, the problem arisesthat hydraulic vibrations can occur, which detract from the shiftingcomfort and shorten the service life. It is possible to reduce or evenprevent the occurrence of these vibrations among other things by meansof throttle restrictions in the form of apertures placed between thehydraulic actuators. Apertures between pressure regulators and followervalves are particularly suitable means for these vibrations. Theseapertures are usually accommodated structurally somewhere in the linesbetween the pressure regulator and the consumer or in a so-calledintermediate plate. The apertures are usually provided in a positiondetermined based on structural circumstances, between the pressureregulator and a follower valve, in a passage through an intermediateplate.

SUMMARY OF THE INVENTION

The solenoid valve according to the invention, in particular for anautomatic transmission, has the advantage over the prior art that athrottle restriction is provided in a simple manner by being integratedinto the solenoid valve. The position of the throttle restrictionrelative to the solenoid valve is unambiguously established due to itsintegration into the solenoid valve so that it is placed at the positionof its greatest effectiveness, which reduces application costs for themanufacturer of the hydraulic control system.

It is particularly useful to provide the throttle restriction in theconsumer connection or working pressure connection of a filter cage ofthe solenoid valve. For technical manufacturing reasons, the throttlerestriction is particularly easy to produce at this location.

The filter cage produces a seal between the pressure chamber in whichthe working pressure is generated inside the solenoid valve and areceiving bore for the solenoid valve. An oil exchange can only occurvia the integrated aperture. It is very easy to adapt the losscoefficient of the throttle restriction to the given requirements bychanging its diameter and length.

Integrating the throttle restriction into the filter cage reduces thecost of the entire system since the throttle restriction is lessexpensive to produce in the filter cage than in an intermediate plate.Since the effectiveness of the throttle restriction in the filter cagedepends on the relative position or distance from the solenoid valve,the placement of the throttle restriction according to the inventionallows its diameter to be selected as larger than in an intermediateplate. This gives it a decisive functional advantage at low temperaturessince this shortens the so-called step response times.

Alternatively, the throttle restriction can also be integrated directlyinto the connection fitting or flange of the solenoid valve.

Another advantage of the solenoid valve according to the invention isthat as part of the development and manufacturing process, it can betested together with the throttle restriction that exerts a powerfulinfluence on the valve hydraulics, a combined testing that results in aperceptible quality improvement.

A special shaping of the throttle restriction (e.g. step-shaped,conical, etc.) in order to optimize the dynamic behavior is easier toproduce through the plastic injection-molding technique of the filtercage than it is to produce in an intermediate plate by means of astamping or drilling tool.

There are other possible applications in which the orientation of thethrottle restriction in the circumference direction is crucial foroptimizing the functioning of the throttle restriction. In such cases,the filter cage and the valve part can be provided with a rotationprevention means.

Other advantages and advantageous modifications of the invention ensuefrom the dependent claims and the description.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is shown in the drawing andwill be explained in detail in the description that follows.

The sole FIGURE shows a longitudinal section through a solenoid valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sole FIGURE shows a solenoid valve 10, in particular for use inautomatic transmissions of motor vehicles. In the current exemplaryembodiment, the solenoid valve 10 is used as a pressure regulating valvefor controlling actuators in automatic transmissions. Alternatively, itcan also be an electromagnetically pilot-operated valve.

The solenoid valve 10 has a magnet part 12 and a valve part 14 disposedflush with it. The magnet part 12 essentially includes housing 16, acoil 18, and a movable armature 20 that contains an armature rod 22. Thevalve part 14 is connected to the magnet part 12 by means of aconnection fitting 24. In addition to the connection fitting 24, thevalve part 14 also has an actuating element 26 and a ball-shaped closingelement 28. The connection fitting 24 is provided with an inlet 30, areturn 32, and a consumer connection 34. The armature 20 causes theactuating element 26 to move. The closing element 28 is situated insidethe inlet 30 and is actuated by a tappet 36 disposed inside theactuating element 26. The tappet 36 acts on the closing element 28 byreaching through a bore 38 provided between the inlet 30 and a pressurechamber 40 of the consumer connection 34, in which the working pressureis generated inside the solenoid valve 10. Inside the pressure chamber40, the tappet 36 passes through a baffle plate 41. The tappet 36extends further through the pressure chamber 40 and a bore 42 providedbetween the pressure chamber 40 and the return 32, and is finallyfastened inside the actuating element 26. The actuating element 26 canopen and close the bore 42.

A filter cage 44 is provided on the valve part 14. The filter cage 44 isessentially cup-shaped; the filter cloth 48 is placed at the bottom 46and the annular wall 50 seals off the pressure chamber 40 except for athrottle restriction 52, for example in the form of an aperture,provided in the wall 50. The throttle restriction 52 is integrated intothe filter cage 44 and consequently into the solenoid valve 10. Thisoffers advantages with regard to the precision of the damping action andthat of the manufacture. The fact that the throttle restriction 52 isintegrated into the solenoid valve 10, not spaced apart from it by adistance that varies according to structural dictates as a function ofthe different installation positions, permits better control of thedamping action. Since the filter cage 44 is a plastic injection-moldedpart, the throttle restriction 52 can easily be provided duringmanufacture.

Alternatively, it is also possible to integrate the throttle restriction52 into the pressure chamber of the valve part 14. As in the currentexemplary embodiment, with a solenoid valve 10 that is embodied as aplastic injection-molded part with a correspondingly embodied slidevalve, this integration can be achieved during manufacture. It is alsopossible for the throttle restriction 52 not to be provided in thefilter cage 44 itself. For example, if a filter cage 44 is not required,then with the solenoid valve 10, the throttle restriction 52 can beintegrated into a sleeve that is placed around the pressure chamber 40.

The filter cage 44 or alternatively a sleeve is fastened to the valvepart 14 in a rotationally fixed manner. To this end, a projection 54 isprovided on the filter cage 44 or alternatively on the sleeve, and acorresponding recess 56 is provided on the valve part 14. However, arecess can also be provided on the filter cage 44 or alternatively onthe sleeve. The projection 54 can, for example, be embodied as a lug orrib and the recess can be embodied as a depression or groove. However,other possibilities for preventing rotation are also conceivable.

The throttle restriction 52 has a diameter of approx. 1 mm, and thelength is somewhat shorter than this. However, it is possible to useexperimentation, for example, to determine the optimal ratio of lengthto diameter for each intended application. In addition, it is notabsolutely necessary for the throttle restriction 52 to have a roundcross section. Conical and stepped diametrical progressions are alsoconceivable. It is important that the throttle restriction 52 beintegrated into the solenoid valve 10, on the part of the solenoid valve10 oriented toward the consumer.

1. A solenoid valve (10), for automatic transmissions, comprising, amagnet part (12) and a valve part (14), wherein an actuating element(26) that is actuatable by an armature (20) of the magnet part isdisposed in the valve part (14), wherein the valve part has a pressurechamber (40) and a connection fitting (24) with an inlet (30), a return(32), and a consumer connection (34) branching off from the pressurechamber, and wherein between the pressure chamber and the return, afirst bore is formed, wherein said first bore is closeable by theactuating element, wherein between the pressure chamber and the inlet, asecond bore is formed, wherein said second bore is closeable by aclosing element actuated by the actuating element, wherein a throttlerestriction (52) is integrated into the solenoid valve (10) between theconsumer connection (34) and the pressure chamber (40).
 2. The solenoidvalve (10) according to claim 1, wherein the throttle restriction (52)is formed on a filter cage (44) associated with the valve part.
 3. Thesolenoid valve (10) according to claim 2, wherein the throttlerestriction (52) is provided in a wall (50) of the filter cage (44) thatencompasses a pressure chamber (40) of the valve part.